Modern mobile communication tends to provide users with multimedia services transmitted at a high speed. FIG. 1 is a schematic diagram illustrating architecture of a System Architecture Evolution (SAE).
A User Equipment (UE) 101 is a terminal device for receiving data. An Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) 102 is a Radio Access Network (RAN). The RAN includes a macro eNodeB/NodeB. The macro eNodeB/NodeB provides the UE with a radio network interface, with which the UE may access the radio network. A Mobile Management Entity (MME) 103 is responsible for managing a mobile context, session context and security information of the UE. A Serving GateWay (SGW) 104 mainly provides a function of a user plane. The MME 103 and SGW 104 may be located at a same physical entity. A Packet Data Network Gateway (PGW) 105 is responsible for charging and lawful interception, etc. The PGW 105 and SGW 104 may be located at a same physical entity. A Policy and Charging Rule Function (PCRF) 106 provides Quality of Service (QoS) policies and charging rules. A Serving General Packet Radio Service (GPRS) Support Node (SGSN) 108 is a network node device, which provides data transmission with routing in a Universal Mobile Telecommunications System (UMTS). A Home Subscriber Server (HSS) 109 is a home sub-system of the UE and is responsible for protecting user information. The user information includes a current position of the UE, an address of a serving node, user security information and packet data context of the UE, etc.
The Generation Partnership Project (3GPP) proposes a requirement of small cell enhancement in Rel-12. A target scenario of the small cell enhancement includes: a scenario covered by a macro cell, a scenario, which is not covered by the macro cell, indoor and outdoor enhancement, ideal and non-ideal return enhancement, as shown in FIG. 2.
In the scenario covered by the macro cell, a technology for using inter-eNB carrier aggregation is proposed. The macro cell and small cell may work at different bands. There may be two kinds of architecture of the technology for using the inter-eNB carrier aggregation. In the first kind of architecture, user plane data is separated with a Radio Access Network (RAN). In the second kind of architecture, the user plane data is separated with a Core Network (CN). In the architecture, in which the user plane data is separated with the CN, as for a bearer established in a Pico cell, the data is directly sent to the Pico cell via the SGW in the CN and the user plane data is not forwarded via the macro cell.
In the architecture of the small cell, the UE may simultaneously receive or transmit data on two eNBs, which is called dual-connectivity. In the two eNBs, only one eNB is responsible for transmitting a Radio Resource Control (RRC) message to the UE and responsible for interacting with a control plane entity of the CN which is MME. The above eNB is called a MeNB and the other eNB is called a Secondary eNB (SeNB). A cell of the UE on the MeNB is a Primary cell (Pcell) of the UE. A Radio Resource Control (RRC) message is sent to the UE via the Pcell and the other cells are Secondary cells (Scell)s. A Scell of the UE in the SeNB is a pScell. The pScell has an Uplink (UL) physical layer control channel and the other S cells do not have the UL physical layer control channel A cell group in the MeNB is a Master Cell Group (MCG) and a cell group at the SeNB is a Secondary Cell Group (SCG). Resources of the SCG at the UE side are configured by the SeNB and the SeNB sends configurations of the UE to the MeNB via an RRC container. The MeNB sends the configurations of the UE to the UE. The MeNB does not parse the RRC container or the MeNB parses the RRC container but does not change the configurations of the RRC container.